Question

我有多个模型类，它们共享相同的属性。出于这个原因，我创造了一个特征，例如：

trait Player extends Temp {

  val gameId: BSONObjectID

  val personalDetails: abc.PersonalDetails // <- comes from shared library

}

case class FootballPlayer(var _id: Option[BSONObjectID] = None,
                         gameId: BSONObjectID,
                         personalDetails: abc.PersonalDetails,
                         var created: Option[DateTime] = None,
                         var updated: Option[DateTime] = None
                        ) extends Player

case class VideogamePlayer(var _id: Option[BSONObjectID] = None,
                         gameId: BSONObjectID,
                         personalDetails: abc.PersonalDetails,
                         var created: Option[DateTime] = None,
                         var updated: Option[DateTime] = None
                        ) extends Player

所有这些模型都定义了伴随对象play.api.libs.json.Reads和play.api.libs.json.OWrites。

例如：

object FootballPlayer {

  import play.api.libs.functional.syntax._
  import play.api.libs.json.Reads._
  import play.api.libs.json._
  import reactivemongo.play.json.BSONFormats.BSONObjectIDFormat

  implicit val footballPlayerReads: Reads[FootballPlayer] = (
    (__ \ "_id").readNullable[BSONObjectID].map(_.getOrElse(BSONObjectID.generate)).map(Some(_)) and
      (__ \ "gameId").read[BSONObjectID] and
      (__ \ "personalDetails").read[abc.PersonalDetails] and
      (__ \ "created").readNullable[DateTime].map(_.getOrElse(new DateTime())).map(Some(_)) and
      (__ \ "updated").readNullable[DateTime].map(_.getOrElse(new DateTime())).map(Some(_))
    ) (FootballPlayer.apply _)


  implicit val sharedPersonalDetailsWrites: Writes[abc.PersonalDetails] = abc.PersonalDetails.sharedPersonalDetailsWrites

  implicit val footballPlayerWrites: OWrites[FootballPlayer] = (
    (__ \ "_id").writeNullable[BSONObjectID] and
      (__ \ "gameId").write[BSONObjectID] and
      (__ \ "personalDetails").write[abc.PersonalDetails] and
      (__ \ "created").writeNullable[DateTime] and
      (__ \ "updated").writeNullable[DateTime]
    ) (unlift(FootballPlayer.unapply))

}

现在我想将它们存储在不同的集合中，但我想只有一个DAO，所以我实现了以下内容：

trait PlayerDAO[T <: Player] {

  def findById(_id: BSONObjectID)(implicit reads: Reads[T]): Future[Option[T]]

  def insert(t: T)(implicit writes: OWrites[T]): Future[T]

}

class MongoPlayerDAO[T <: Player] @Inject()(
                                           playerRepository: PlayerRepository[T]
                                         ) extends PlayerDAO[T] {

  def findById(_id: BSONObjectID)(implicit reads: Reads[T]): Future[Option[T]] = playerRepository.findById(_id)

  def insert(t: T)(implicit writes: OWrites[T]): Future[T] = playerRepository.insert(t).map(_ => t)

}

然后，我有以下存储库：

class PlayerService[T <: Player] @Inject()(playerDAO: PlayerDAO[T])(implicit reads: Reads[T], writes: OWrites[T]) {

  def findById(_id: BSONObjectID): Future[Option[T]] = playerDAO.findById(_id)


  def save(t: T): Future[T] = playerDAO.save(t)

}

我的模块如下所示：

class PlayerModule extends AbstractModule with ScalaModule {

  def configure() {
    bind[PlayerDAO[FootballPlayer]].to[MongoPlayerDAO[FootballPlayer]]
    bind[PlayerDAO[VideogamePlayer]].to[MongoPlayerDAO[VideogamePlayer]]
    // ...
    ()
  }
}

在我的Play控制器中，我注入了以下内容：

import models.FootballPlayer._
import models.VideogamePlayer._ 

class PlayerController @Inject()(
                                 val messagesApi: MessagesApi,
                                 footballPlayerService: PlayerService[FootballPlayer],
                                 videogamePlayerService: PlayerService[VideogamePlayer]
                               ) extends Controller with I18nSupport

然而，不幸的是，我得到以下例外：

1）没有实施 play.api.libs.json.OWrites被绑定了。 2）没有 play.api.libs.json.OWrites的实现受到约束。 3）没有实施 play.api.libs.json.Reads被绑定了。 4）没有 play.api.libs.json.Reads的实现被约束了。

我该如何解决这个问题？

Answer 1

当进行dao注射时，可能无法找到隐含的上下文。尝试在您定义绑定的AbstractModule中包含implicits。

修改

在git上检查我的解决方案。 Here

我试图效仿你想做的事情和工作正常。

我不太确定您当前代码的问题是什么，因为我无法访问整个代码，但我认为它与搜索OWrites的应用程序和隐含Player的读取有关。比FootballPlayer或VideoGamePlayer

在Scala Play应用程序中没有绑定OWrites和Reads的实现

1 个答案: